Rotary mowers, such as push or riding lawnmowers, have high-speed rotating blades that are generally covered by a metal deck that prevents the mower from throwing objects (e.g., grass clippings, sticks, stones, and other objects that the mower encounters in the lawn) and at least tries to prevent contact between a person and the moving blades. One problem with the use of a deck is that some lawn clippings, referred to herein as “thatch,” accumulates on the underside of the deck. In some circumstances, the amount of built-up thatch is so great that movement of the rotating blades is disrupted or even stopped. Removal of the thatch can be difficult due to the wet, sticky nature of the material, especially in curved portions of an underside of the deck.